The invention relates to a lubricating circuit for a tilting power transmission box, of the type generally intended to rotate at least one driven assembly about an axis of rotation itself having to be able to swivel, during the rotation of the driven device, about a tilting axis, more or less perpendicular to the axis of rotation of driven device, with said transmission box including a tilting crankcase assembled about the tilting axis on a rigid non-tilting support.
The tilting transmission crankcase can be used, in a nonrestrictive way, as power transmission crankcase to equip aircraft whose system of propulsion is directional, such as dirigibles or aircraft of the convertible type, in which case the rotation of the driven device by the transmission is ensured from at least one rotational power source, or yet again as power transmission box fitted to windmills, in which case the driven device is a rotor spun by the wind, and is actually a driving force for the transmission which drives a receiver, for example, an alternator.
Generally, the tilting power transmission box lubricated by the installation according to the invention may be used in all the directional propulsion or energy generation systems by rotation which require, for their smooth operation, effective lubrication of the transmission system placed in the tilting crankcase, such as driving gears, bearings and/or driving ribs.
In particular, as an application for which a tilting power transmission box equipped with a lubrication installation according to the invention is of great interest to the Applicants, such a transmission box can be used for driving in rotation, from at least one motor-propulsion unit, for example of the turbomotor type, at least one tilting rotor of an aircraft of the type known as convertible, being able to operate in aircraft mode or helicopter mode, and whose rotor drive shaft turns about a tilting axis so as to be able to change from a position in which the rotor functions like a propeller for flight in aircraft mode to a position in which the rotor functions like a helicopter hovering rotor for the helicopter flight mode.
A tilting power transmission box for such a convertible tilting rotor aircraft is described in particular in FR 2 791 319 and FR 2 791 634, to be referred to for more precise on this subject However, note that these two patents describe a convertible tilting rotor aircraft, of a type in which each rotor shaft turns about itself through a reducing assembly in front of respectively one of two power transmissions each comprising also a rear reducing unit, connected to the corresponding front reducing unit and to respectively two engines (turbomotors), each supported by respectively one of the two fixed wings of the aircraft, and with an interconnecting shaft connecting the two transmissions for the rotational driving of the two rotors by either of the two engines, in the event of the other engine failing.
Each rotor shaft, the corresponding power transmission and the corresponding engine are placed in one respectively of two articulated nacelles, each comprising a front part designed to tilt, about the tilting axis, on a fixed part with respect to the aircraft and attached respectively to the two wings of the aircraft, in which are placed the corresponding engine and at least part of the rear reducing unit of the corresponding transmission, of which the front reducing unit, engineered like a main helicopter transmission box and the corresponding rotor shaft are housed in the front tilting part of the nacelle, and are assembled to tilt with this front part compared to the rear fixed part of the nacelle and the corresponding fixed wing.
In this application, and with this architecture, for each power transmission, it is essential that many of the parts of the front reducing unit, housed in the tilting crankcase, are constantly suitably lubricated, when the rotor turns, to ensure the safe flight of the aircraft.